Replacing a teacher in the bottom 5% with an
average one will
boost a student's estimated lifetime income by
$250,000.

Having a great teacher, one
that's a standard deviation (SD) better than the
median for one
grade boosts a
student's income at age 28 by an average of 1.3%

This according to a new series of working papers (I
and
II) from John Bates Clark medal winner Raj Chetty, and
coauthors Jonah Rockoff and John Friedman. They find
primary school students who had better teachers are more likely
to go to college, go to better schools, earn more money, and are
less likely to have children as teenagers.

Figuring out how to measure
teacher quality is controversial. Right now, places like Los
Angeles and Washington, D.C. are just starting to measure
teachers by value added metrics (VA), the amount that they boost
test scores.

The first
paper in the series finds that the ability to boost
test scores is a useful measure of teacher quality, that
differences in scores come from teacher ability, not student
sorting. Eighty-five percent of differences in VA are within
schools, not between them. It might be worth considering more
broadly.